High frequency tube method and apparatus



Sept. 21, 1965 A. STAPRANS 3,207,943

HIGH FREQUENCY TUBE METHOD AND APPARATUS Original Filed Aug. 6, 1959 2 Sheets-Sheet l INVENTOR ARMAND STAPRANS P 1965 A. STAPRANS 3,207,943

HIGH FREQUENCY TUBE METHOD AND APPARATUS Original Filed Aug. 6. 1959 2 Sheets-Sheet 2 Fig.4

' l 6% f +6% I,- INVENTOR FREQUENCY DEVIATION ARMANI) STAPRANS ATTORNEY United States Patent 3,207,943 HIGH FREQUENCY TUBE METHOD AND APPARATUS Armand Staprans, 2455 Beth; Ave., Mountain View, Calif. Original application Aug. 6, 1959, Ser. No. 832,402, now Patent No. 3,169,206, dated Feb. 9, 1965. Divided and this application Aug. 29, 1962, Ser. No. 220,327

4 Claims. (Cl. 3155.43)

The present invention is a divisional application divided out of copending application U.S. Serial No. 832,402 filed August 6, 1959, and now issued as US. Patent No. 3,169,206 on February 9, 1965, and relates in general to high frequency tubes and more particularly to a novel high power, pulsed, hi, broad band amplifier useful, for example, in applications as navigation and communication systems, as a driver for a linear accelerator, and the like.

The present invention is directed to .a novel high frequency high power klystron amplifier. The tube comprises a phf. seven cavity cariable tuned klystron amplifier having a 45% RP. efficiency and providing a 3% one-half power bandwidth tunable over a 12% full power range. This tube is approximately nine feet long and including only the evacuated structure weighs approximately seven hundred pounds. The tube will deliver 8 megawatts peak R.F. energy with an average power of approximately 30 kw.

The principal object of the present invention is to provide an improved high frequency klystron amplifier tube apparatus which is relatively simple of construction, relatively easy to handle, and which will have long operating life while delivering high peak and high average RF. power.

One feature of the present invention is the provision of a low capacity broadband coupling slot for coupling high R.F. power from the output cavity to an output waveguide without adjustment over a relatively broad band of frequencies.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein,

FIG. 1 is a longitudinal view, partly in section, showing the multicavity klystron amplifier apparatus of the present invention,

FIG. 2 is a cross sectional view of the structure of FIG. 1 taken along line 22 in the direction of the arrows,

FIG. 3 is an enlarged cross sectional view of a portion of the structure of FIG. 1 taken along line 3-3 in the direction of the arrows,

'FIG. 4 is a typical graph of energy transmission versus frequency deviation for the coupling structure shown in FIG. 3, and

FIG. 5 is an enlarged cross sectional view of a portion of the structure of FIG. 1 taken along line 55 in the direction of the arrows.

Referring now to FIG. 1 there is shown a longitudinal partly cross sectional view of a high frequency high power multicavity klystron tube apparatus utilizing features of the present invention. More specifically, the tube comprises an elongated tubular metallic envelope 1 having an electron gun assembly 2 at one end thereof for producing and directing the beam of electrons axially through the elongated vacuum envelope 1 to an electron collector assembly 3 mounted at the other end of the elongated envelope 1. A plurality of cavity resonators 4 are provided between the cathode assembly 2 and the collector assembly 3 for successive electromagnetic interaction with the beam of electrons passable therethrough.

A beam focusing solenoid 5 envelopes the central portion of the tubes envelope for focusing the electron beam throughout the length of the tube apparatus. The free end portion of the cathode assembly 2 is inserted within an oil tank 6 and sealed therewithin via suitable mating flanges provided on the tube envelope 1 and the oil tank 6. The oil in the oil tank serves to prevent electrical breakdown across the high voltage anode to cathode insulator of the cathode assembly 2.

Electromagnetic energy which it is desired to have amplified by the tube is fed to the first cavity 4 of the tube via coaxial line 7 and input loop 8. This R.F.

energy serves to velocity modulate the beam, such velocity modulation being transformed into current density modulation as the beam travels down the length of the tube. The current density modulation is further enhanced by successive cavities 4. The current density modulation serves to excite the last or output cavity 4. The greatly amplified R.F. output energy is extracted from the output cavity 4 via a suitable coupling iris 10 and hollow waveguide 9. The waveguide 9 is wrapped around the collector assembly 3. The output R.'F. energy is extracted from the waveguide 9 via a coaxial line 11 and thence fed via a doorknob transition 12, having a cylindrical wave permeable window 13 vacuum sealed therein, to an output rectangular Waveguide 14.

Referring now to FIGS. 3 and 5 there is shown a novel broad band low capacitance coupling iris 10 utilized for coupling wave energy from the output cavity 4 to the wrapped-around waveguide 9 in the tunable seven cavity klystron amplifier model of the present invention. More specifically, the transverse wall of the output cavity 4 formed by the pole piece 107 is provided with a coupling iris 10 in the form of a portion of an annular slot 127 which subtends approximately of circumferal are about the longitudinal axis of the tube. The coupling slot 127 is symmetric with respect to a radius extending at an angle of 30 to the vertical to oifset the RF. coupling effect of the tuner assembly 21 primarily due to the capacitive tuning plate 22. The central portion of the coupling slot 127 is enlarged radially outwardly at 1253 thereby decreasing the capacitive reactance of the iris 10 as compared to the capacitive reactance of a coupling iris having a uniform height.

Decreasing the capacitive reactance of the iris 10 not only raises its resonant frequency but tends to decrease the Q of the coupling iris 10 whereby greater bandwidth may be obtained. In this particular tunable tube model of the present invention it was desirable to have a broadband coupling iris coupling the output cavity 4 to the load. Moreover, it was desirable that this coupling iris have an increasing coupling effect with increasing frequency to compensate for decreasing interaction between the output cavity 4 and the beam with increasing frequency whereby uniform R.F. coupling to the load could be obtained over a wider band of frequencies. Therefore, the resonant frequency f, of the iris 10 was selected slightly higher than the tunable range of the tube (see FIG. 4), the resonant frequency of the output cavity 4 being tunable over the 12% band and the resonant frequency of the cavity 4 being f In other applications it may be desirable to provide an output iris 10 with a decreasing coupling coefiicient with increasing frequency in which case the resonant frequency f, of the broadband iris 10 would be selected slightly lower than the tunable range of the tube. In the particular seven cavity tunable klystron model of the present invention, the output coupling iris 127 provided the desired coupling characteristic for the output cavity over a 12% bandwidth while passing 10 megawatts peak and 30 kw. average power. In a particular exemplary coupling iris 10 the pole piece 107 was approximately one inch thick,

the height of the narrow slot portion 127 of the iris 10 was approximately one inch and the height of the central large poriton 128 of the iris 10 was approximately 2.6". The iris 10 fed the output waveguide 9 having amean radius of approximately five inches and a height of .approximately 2.6".

Since many changes could be made in the above construction and many apparently widely ditferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A high frequency tube apparatus including, means for producing and directing a beam of electrons over a predetermined path longitudinally of the tube, means forming an electromagnetic wave supporting structure disposed along said beam path for electromagnetic interaction with the beam, means form a vacuum-tight envelope enclosing the beam path, said wave supporting structure including a chamber having a conductive wall member, means for coupling wave energy from said chamber portion of said wave supporting structure for propagation to a suitable load, said coupling means including an iris formed in said conductive wall member of said chamber for passage of electromagnetic energy therethrough, said iris being elongated in transverse section and having a central portion of increased height whereby the capacitance of said iris is decreased as compared to an iris of constant height thereby increasing the coupling bandwidth of said iris and the operating bandwidth of the tube apparatus.

2. A high frequency kly-stron tube apparatus including, means for forming and projecting a beam of electrons over an elongated beam path, collector means disposed at the terminal end of the beam path for collecting and dissipating the energy of the beam, means forming a plurality of cavity resonators disposed along said beam path for successive electromagnetic interaction with the beam, means for coupling wave energy to one of said resonators forming an input resonator for applying signal energy to be amplified to said beam, means forming an output coupling network coupled to a second one of said resonators forming an output resonator disposed downstream of said input resonator for extracting amplified signal wave energy from said beam, said output coupling means including an iris formed through the wall of said output resonator for passage of amplified signal Wave energy therethrough to a suitable load, said iris being elongate-d in transverse section and having a central portion of increased height whereby the capacitance of said iris is decreased as compared to an iris of constant height thereby increasing the coupling bandwidth of said iris and the operating bandwidth of the tube apparatus.

3. The apparatus according to claim 2, wherein said output resonator structure includes a chamber having a pair of longitudinally spaced end walls interconnected by a side wall structure, and wherein said iris is formed in the downstream end wall of said resonator chamber, said iris being curvilinear, and an output tubular wave guide section being disposed in registry with said curvilinear iris and being longitudinally directed of the beam path, and being partially wrapped around the beam path and said collector means.

4. The apparatus according to claim 2 wherein said tube has a tunable operating band over a certain predetermined bandwidth and wherein said output coupling iris has a resonant frequency disposed outside of said tunable operating bandwidth of the tube apparatus to provide a desired frequency dependent coupling characteristic.

References Cited by the Examiner UNITED STATES PATENTS 2,815,467 12/57 Gardner 33383 2,956,200 10/60 Bates 3 l5-3.6

2,970,242 1/ 61 Jepson 315-539 DAVID J. GALVIN, Primary Examiner. 

1. A HIGH FREQUENCY TUBE APPARATUS INCLUDING, MEANS FOR PRODUCING AND DIRECTING A BEAM OF ELECTRONS OVER A PREDETERMINED PATH LONGITUDINALLY OF THE TUBE, MEANS FORMING AN ELECTROMAGNETIC WAVE SUPPORTING STRUCTURE DISPOSED ALONG SAID BEAM PATH FOR ELECTROMAGNETIC INTERACTION WITH THE BEAM, MEANS FORM A VACUUM-TIGHT ENVELOPWS ENCLOSING THE BEAM PATH, SAID WAVE SUPPORTING STRUCTURE INCLUDING A CHAMBER HAVING A CONDUCTIVE WALL MEMBER, MEANS FOR COUPLING WAVE ENERGY FROM SAID CHAMBER PORTION OF SAID WAVE SUPPORTING STRUCTURE FOR PROPAGATION TO A SUITABLE LOAD, SAID COUPLING MEANS INCLUDING AN IRIS FORMED IN SAID CONDUCTIVE WALL MEMBER OF SAID CHAMBER FOR PASSAGE OF ELECTROMAGNETIC ENERGY THERETHROUGH, SAID IRIS BEING ELONGATED IN TRANSVERSE SECTION AND HAVING A CENTRAL PORTION OF INCREASED HEIGHT WHEREBY THE CAPACITANCE OF SAID IRIS IS DECREASED AS COMPARED TO AN IRIS OF CONSTANT HEIGHT THEREBY INCREASING THE COUPLING BANDWIDTH OF SAID IRIS AND THE OPERATING BANDWIDTH OF THE TUBE APPARATUS. 